The global biodiesel market demand is estimated to reach 37 billion gallons by 2016, growing at an average annual growth rate of 42%. Europe will be the major market for the next decade or so, closely followed by the US market. To meet this increased market demand, additional oil sources, especially non-edible oils, need to be explored (Li et al., 2008 Appl. Microbiol. Biotechnol. 80:749-756). Microalgae seems to be the only source of renewable biodiesel that has the potential to displace petroleum-derived transportation fuels without the controversial argument “Food or Fuel” and to help the nation reach the 2003 Biofuels Directive target of achieving greenhouse gas savings (Christi, 2007, Biotechnol. Adv. 25:294-306; Christi, 2008, Trends Biotechnol. 26:126-131; Cockerill and Martin, 2008, Biotechnol. Biofuels 1:9).
The most advanced biotechnology being applied to algal growth has been the creation of the antennae mutants that have less light harvesting machinery in the cell, which allows a greater fraction of the light to pass through an individual cell. This light then strikes other cells deeper in the culture. This is viewed as advantageous because some of the light energy striking a normal cell is in excess and is lost as fluorescence. These mutants do not suffer this loss of excess energy; it is available to other deeper cells in the culture. Thus the overall culture accumulates biomass faster. These mutants then grow using their normal rates of metabolism. In addition, some are attempting to engineer herbicide resistance genes into the production strains to allow competing algae in a production bioreactor to be controlled with the herbicide.
Numerous algal biofuels companies populate the landscape; it is reasonable to expect at least 20 of them will be producing algal oil at large scale within a year. Microalgal biodiesel is technically feasible (Gouveia et al. 2009 J. Ind. Microbiol. Biotechnol 36:269-274). However technoeconomic analyses show that for microalgal biofuels to be economically competitive with petrodiesel, the production, harvesting and extraction steps must be optimized and costs reduced. The production step must be increased substantially to increase the overall total biomass production. The degree to which the production rate can be improved within the constraints of the fixed costs of the production reactor, will dictate how much other costs must be reduced to achieve profitability or even the bottom line. The technology described herein can be expected to address that need.
In plants, the organic compound 2-oxoglutaramate is a powerful signal metabolite which regulates the function of a large number of genes involved in the photosynthesis apparatus, carbon fixation and nitrogen metabolism. A number of transaminase and hydrolyase enzymes known to be involved in the synthesis of 2-hydroxy-5-oxoproline in animals have been identified in animal liver and kidney tissues (Cooper and Meister, 1977, CRC Critical Reviews in Biochemistry, pages 281-303; Meister, 1952, J. Biochem. 197:304). In algae, the biochemical synthesis of 2-hydroxy-5-oxoproline has not been established. Moreover, the function of 2-hydroxy-5-oxoproline in algae is unknown.
Unkefer et al., U.S. Pat. No. 6,593,275, disclose a dramatic increase in the growth rate of algae when treated with 2-hydroxy-5-oxoproline. Continuously culturing the algae in the presence of this compound or mixtures of this compound with other prolines will enrich sub-strains of the algae that respond well to the prolines.